Abstract
Background: Urban wildlife has been increasing during the last years, however the effect of urbanization on it is poorly understood. The common opossum (Didelphis marsupialis) is very frequent in the Metropolitan Area of Valle del Aburrá (AMVA), in Antioquia, Colombia, where there is also a strong opossum-human conflict that results in a large number of injured/dead opossums. Objective: We evaluated the effects of urban and rural habitats on the morphometry and the reproductive output (litter size in marsupium) of opossums. Methods: A total of 131 opossums were captured, 94 from the AMVA, and 37 from rural areas of Antioquia. Opossums were weighed, measured, sexed, clinically inspected, and photographed. Results: Urban opossums were heavier and larger than rural individuals, regardless of sex, and there were no differences in the reproductive output between the two habitats. Also, urban opossums were more abundant than rural opossums. A potential explanation of these results is that cities favor survival mediated by higher food consumption, but not reproduction. Alternatively, bigger animals could also be explained by an inadequate food consumption rich on carbohydrates which may have potential negative health consequences. We confirmed the sexual size dimorphism of the common opossum in the head and tail lengths but not on the body length. Conclusion: We confirm a significant effect of urban environments on body mass and size of opossums; however, it is unknown whether it is beneficial or detrimental. Litter size is the lowest reported for the species, and there was no difference between rural and urban habitats.